Three-dimensional semiconductor packages become essential for a higher density and larger capacity. The three-dimensional packaging technology is by thinning semiconductor chips, and laminating them in multilayer structure while providing through silicon via (TSV) interconnects. For realizing the above, it is required to conduct the steps of thinning a substrate having a semiconductor circuit formed thereon by grinding its non-circuit-forming surface (it is also called as “back surface”), and further forming electrodes including TSV on the back surface. In the prior art, prior to the step of grinding the back surface of a silicon substrate, a protective tape is adhered to the back surface of the substrate opposite to the surface to be ground for preventing the wafer from breakage during the grinding step. However, this tape uses an organic resin film as a base material, it is flexible, but is insufficient in strength and heat resistance to withstand the TSV forming step and the step of forming interconnects on the back surface so that it is not suitable.
It is then proposed to bond a semiconductor substrate to a support such as silicon and glass via an adhesive layer whereby it becomes a system to sufficiently withstand the steps of grinding a back surface, and forming TSV or electrodes on the back surface. The adhesive layer is important for this system to bond the substrate to the support. The adhesive layer is required to bond the substrate to the support without leaving gaps, to have sufficient durability which can withstand the subsequent steps, and eventually allow the thin wafer to be easily delaminating from the support. The adhesive layer is thus finally removed so that, in the present specification, the adhesive layer is referred to as a temporary adhesive layer (or a temporary adhesive material layer).
With regard to the conventionally known temporary adhesive layers and a removing method thereof, there have been proposed a technique in which high intensity light is irradiated to an adhesive material containing a light absorbing substance to decompose the adhesive material layer whereby the adhesive material layer is peeled from the support (Patent Literature 1), and a technique in which a heat fusible hydrocarbon type compound is used as an adhesive material, and bonding and delaminating are carried out in a heat-molten state (Patent Literature 2). The former technique involved the problems that it requires an expensive tool such as laser, and a treatment time per one substrate is longer. The latter technique is simple because of control only by heat, but the applicable range is limited since thermal stability at high temperatures exceeding 200° C. is insufficient. Further, these temporary adhesive layers are not adequate to form a layer with uniform thickness on a heavily stepped substrate and to provide a complete adhesion to the support.
It has also been proposed to use a silicone adhesive agent as the temporary adhesive material layer (Patent Literature 3). This is to bond a substrate to a support using an addition curable type silicone adhesive agent, and on removal, the assembly is immersed in a chemical solution capable of dissolving or decomposing the silicone resin, whereby the substrate is separated from the support. Thus, this method takes a very long time for removal and is difficulty applicable to the actual manufacturing process.